In the field of electronic materials, materials for flexible printed circuit (FPC) boards such as cover lays and flexible metal-clad laminated plates have been heretofore used in which a resin layer having electric insulation quality, such as a polyimide film or a polyamide film; an adhesive layer mainly composed of an epoxy resin or a polyimide resin; a metal foil layer having electrical conductivity, such as a copper foil, a silver foil or an aluminum foil; and so on are appropriately combined. As metal-clad laminated plates, two-layer flexible metal-clad laminated plates including a metal layer and a polyimide resin layer, and three-layer flexible metal laminated plates including a metal layer, a polyimide resin layer and an adhesive layer are mainly known.
In recent years, for achieving further downsizing and weight saving of electronic devices, miniaturization of wiring to be provided on a substrate has been promoted, and components to be mounted have been downsized and densified. Thus, the problem may arise that when a large dimensional change occurs after fine wiring is formed, a mounting position of a component is deviated from that in a design stage, so that the component and a substrate are not favorably connected to each other. Heretofore, control of lamination pressure, control of the tension of an adhesion film or the like has been performed as an attempt to suppress a dimensional change. However, although a dimensional change is improved to some extent by the above-mentioned means, the improvement is not sufficient yet, and further suppression of a dimensional change has been desired.
As a means to solve the above-described problem, Patent Document 1 discloses that when a laminated body in which a protecting material and a flexible metal-clad laminated plate are in close contact with each other is conveyed after lamination with a specific tension applied in a machine direction (MD), a dimensional change can be suppressed.
In addition, Patent Document 2 discloses that when the amount of heat at an endothermic peak observed in a glass transition region is adjusted to fall within a specific range, dimensional change ratio caused by thermal shrinkage of a flexible metal foil laminated body and variations in a dimensional change can be reduced, and describes that such a laminated body is obtained by performing heat treatment for 8 hours more at a temperature lower than the glass transition point Tg of resin by 5 to 50° C.